A vehicle may include an engine that may be automatically stopped and restarted without a driver of the vehicle specifically requesting an engine stop and start. The engine may be automatically stopped and restarted to conserve fuel. The engine may be stopped when the driver of the vehicle is not requesting torque while the vehicle is moving or while the vehicle is stopped. Before the engine is automatically stopped, a controller may require that certain conditions be met. For example, the controller may require that electric energy storage device state of charge is higher than a threshold, an electrical load applied to the vehicle electrical system is less than a threshold, electric energy storage device temperature is less than a threshold, and driver demand torque is less than a threshold. If the conditions are met, the engine may be automatically stopped and then restarted to conserve fuel. However, some vehicles may be more frequently automatically stopped and started as compared to other vehicles. Vehicle components used to automatically stop and start the engine may be constructed to provide the engine start/stop functionality over a predetermined vehicle travel distance even when the engine is frequently stopped and started; however, the cost of producing such vehicle components may be prohibitive. Therefore, it would be desirable to provide a way of permitting automatic engine stopping and starting over a predetermined travel distance with reasonable vehicle component cost.
The inventors herein have recognized the above-mentioned issues and have developed a vehicle operating method, comprising: estimating an amount of electric energy storage device useful life consumed via a controller; adjusting automatic engine stop/start thresholds in response to the amount of electric energy storage device useful life consumed; and starting or stopping the engine in response to the automatic engine start/stop thresholds via the controller.
By adjusting automatic engine stopping and starting thresholds in response to an amount of electric energy storage device useful life consumed, it may be possible to decrease frequency and rigorousness of automatic engine stops and starts so that devices may operate over their expected life cycle. Further, automatic engine stopping and starting may still be permitted so that the vehicle's fuel efficiency may be relatively high. In some examples, if the percent of useful life consumed of the device is less than a threshold, the automatic engine stopping and starting thresholds may be returned to base values. In this way, automatic engine stopping and stopping entry conditions may be made more or less rigorous depending on how the engine has been previously stopped and started so that component life may meet expectations while delivering desirable fuel economy.
The present description may provide several advantages. For example, the approach may allow engine components to reach a desired life span. In addition, the approach may allow component life spans to be met without having to make the components suitable for extreme duty cycle conditions. Further, the approach may be applicable to more than one type of component.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.